What is an effective horse rotational deworming program?

The standard 3-way rotation that has been used for years is no longer considered a reasonable way to control parasites in horses. This is because of the development of resistant parasites to the drugs that have been in use so long. There are 4 classes of dewormer on the market in the US:

benzimendazoles --fenbendazole, oxibendazole, other chemicals that end in -azole (there is a long list)

pyrantels---pyrantel pamoate (paste) and pyrantel tartrate (daily dewormer)

avermectins---ivermectin and moxidectin

praziquantel In more than 90% of areas tested strongyles are now resistant to fenbendazole and in more than 40% they are resistant to pyrantel. There has even been 1 study showing strongyles becomeing resistant to ivermectin. So, the standard rotation in that link you are likely not going to be effectively killing strongyles for 1, maybe 2 and even as many as 3 out of 3 dewormings. And the problem is only going to continue to grow. The top equine veterinary parasitologists now recommend strategic deworming rather than simply putting a horse on a rotational deworming program. With a strategic deworming program, parasite contamination of pastures is controlled with 2-4 dewormings per year based upon each horse's own resistance to GI parasites. A wonderful resource for figuring out a deworming program is the strategic deworming webinar available online through The Horse Magazine: http://www.thehorse.com/Video.aspx?vID=183 The veterinarian who presented the topic lays out all the information necessary for a horse owner and veterinarian to work out a strategic deworming program.